MadLeomon is an Undead Digimon whose name and design are derived from "MadLeomon". It is a berserker who lost its intelligence and enhanced its combat instinct. Although it was originally a Lion Digimon, it heaped modification upon modification and arrived at its current appearance. In the process, its consciousness vanished, and it became nothing more than a puppet that defeats those standing before it, as it is commanded. Because it doesn't act or think according to its natural instincts, it exhibits headlong assaults, heedless even of any traps or gadgets. Although it is fundamentally high-powered, its patterns are meager, with nothing but primitive attacks such as hitting and kicking. Nevertheless, caution is necessary, because its sharp claws bear a deadly poison which can cause anything to rot away.[6]

Armed MadLeomon is an Undead Digimon whose name and design are derived from "MadLeomonArmedMode". It is the "Weapon-frenzy Mode" (凶器乱舞形態,Kyoukiranbu Keitai?) of MadLeomon, who gave itself a chainsaw as well as even more modifications. Due to its repeated modifications and unbalanced chainsaw, intense pain is always running through its body, enraging MadLeomon. Because it is unable to stay still, due to its pain, it sees anything reflected in its eyes as an enemy, and attacks.[9]

Digimon Fusion

The Lion Sleeps Tonight: Chops things up without caring whether they are alive or inanimate, while looking as if it is trying to completely shake off its arm and detach the chainsaw. The Lion "Sleeps" when its hunger is satisfied, that is, when it has preyed upon an opponent. In order for the Lion to sleep, it must also defeat that opponent.

Lion Heart: Rampages and pierces the ground with its chainsaw, creating fissures which swallow the opponent. The appearance of the torn and broken ground, caused when Armed MadLeomon's destructive impulses come to the surface, is the very embodiment of its mind.

MadLeomon (Orochimode) is a Digimon whose name and design are derived from "MadLeomonOrochiMode". It is a form of MadLeomon created when it absorbs the data of an Orochimon, growing in size and gaining Orochi's heads for its limbs as well as its tail.

MadLeomon (Final Mode) is a Digimon whose name and design are derived from "MadLeomonFinalMode". It is a form of MadLeomon created when it absorbs the data of several Apemon. MadLeomon grows in size and gains many spikes, while its mane turns red and it loses most of its clothes.